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M D Trifunac - One of the best experts on this subject based on the ideXlab platform.
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coherence of sh waves near a semi circular inclusion the role of interference and standing waves
Earthquake Engineering and Engineering Vibration, 2021Co-Authors: Zaniar Tokmechi, Reza S Jalali, M D Trifunac, M I TodorovskaAbstract:We present examples of a controlled numerical experiment that contribute towards understanding of the physical phenomena that lead to the reduction of coherency of strong Earthquake Ground Motion. We show examples for separation distance of 100 m between the two points on the Ground surface, which is in the range of engineering interest. Our examples illustrate the consequences of: (a) standing waves that result from interference of the incident and reflected waves from a near vertical contrast in material properties, (b) standing waves within a concave inhomogeneity (a semi-circular valley in our examples), and (c) smaller Motions in the diffraction zone, behind the inhomogeneity. We show that it is possible to reduce coherency, to the extent observed for recorded strong Earthquake Ground Motion, even by a single inclusion in a half space, for incident Ground Motion that is coherent. We also illustrate the combined effects of geometric spreading and finite fault width, superimposed on the otherwise dominating effects caused by interference. Our examples show reduction of coherence for specific angles of incident waves, while, for other angles of incidence, the coherence remains essentially equal to one.
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attenuation of strong Earthquake Ground Motion ii dependence on geology along the wave paths from the burmese subduction zone to northeastern india
Soil Dynamics and Earthquake Engineering, 2018Co-Authors: I D Gupta, M D TrifunacAbstract:Abstract This paper presents another example of event-specific, region-specific attenuation equations for strong Earthquake Ground Motion through essentially the same geological region defined by geometrically constrained ray paths. The current study describes strong Motion wave attenuation from deep Earthquakes in the Burmese subduction zone, as recorded by strong Motion accelerographs in northeastern India. The accompanying empirical scaling equations to determine the Fourier and pseudo-relative velocity (PSV) spectra for the same events are also presented. To demonstrate the validity of the long-period extension of the above spectra, independent estimates of peak Ground displacement from recorded accelerograms and estimates of the seismic moment from distant recordings of Earthquakes are shown to be in good agreement with the extended spectral amplitudes. The validity of a short-period extension has been tested by comparing the values of pseudo acceleration spectral amplitudes at short periods with the recorded peak Ground accelerations. Presented Fourier and PSV spectra can thus be considered to provide a sound basis for macro- and micro-zoning specific to the highly seismic regions of northeastern India.
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site conditions and Earthquake Ground Motion a review
Soil Dynamics and Earthquake Engineering, 2016Co-Authors: M D TrifunacAbstract:Abstract Studies of the effects of local site conditions on the amplitudes and duration of strong Earthquake Ground Motion have evolved from observations of Earthquake damage to buildings. Such studies have involved different degrees of detail and sophistication in how scaling parameters are defined and used. We review the frequently used scaling parameters with an emphasis on the volume of site geology and site soil they represent, the assumptions of one-, two-, or three-dimensional modeling of the associated wave Motions, and a linear versus nonlinear site response. We describe the limitations of using only one site parameter, based on the soil properties in the top 30 m, and discuss how the description of site effects could be refined by increasing the number of descriptive parameters and the extent to which those describe deeper geologic structure.
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a note on the power of strong Ground Motion during the january 17 1994 Earthquake in northridge california
Soil Dynamics and Earthquake Engineering, 2013Co-Authors: M D Trifunac, M I TodorovskaAbstract:Abstract Variations of average and maximum power of strong Earthquake Ground Motion during the 1994 Northridge, California Earthquake were gradual and smooth over distances as large as tens of kilometers. Correlation of the contours of recorded power with the depth of sediments and vertical offsets of the basement rocks along the faults in the Los Angeles basin implies a horizontal flow of Earthquake wave energy through the deep waveguides of this basin. If the fault-to-station distances were to be measured along the three-dimensional wave paths through these sedimentary waveguides, rather than along straight lines emanating from the source, as is common in empirical studies of strong Motion amplitudes, the accuracy of empirical-scaling equations for the prediction of the power of strong shaking could improve significantly.
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a note on energy of strong Ground Motion during northridge california Earthquake of january 17 1994
Soil Dynamics and Earthquake Engineering, 2013Co-Authors: M D Trifunac, M I TodorovskaAbstract:Abstract The average contours of spatial variations of energy of strong Earthquake Ground Motion during the 1994 Northridge, California Earthquake change monotonically and slowly over distances as large as tens of kilometers. Comparison of those contours with the depth of sediments and with vertical offsets of the basement rocks along the faults in the Los Angeles basin implies predominantly horizontal flow of energy through the deep wave-guides of the Los Angeles basin. If the source-to-station distances were measured along the three-dimensional wave paths through these sedimentary wave-guides, rather than along straight lines, as is common at present, the accuracy of empirical scaling equations for prediction of strong-Motion energy would be improved significantly.
Izuru Takewaki - One of the best experts on this subject based on the ideXlab platform.
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critical response of elastic plastic sdof systems with nonlinear viscous damping under simulated Earthquake Ground Motions
Heliyon, 2019Co-Authors: Goki Tamura, Kotaro Kojima, Izuru TakewakiAbstract:Abstract Multi impulse with constant time interval is used as a representative of a long-duration Earthquake Ground Motion. An analytical expression is derived for the elastic-plastic response of a single-degree-of-freedom (SDOF) model with nonlinear viscous damping subjected to the "critical multi impulse" which maximizes the response. The fact that only free vibration appears under such multi impulse enables the smart application of an energy approach in deriving the analytical expression for a complicated elastic-plastic response with nonlinear viscous damping. The nonlinear viscous damping characteristic for deformation is approximated in terms of a quadratic or elliptical function. The critical timing of the impulses is found to correspond to the zero restoring-force timing or the maximum velocity timing depending on the input level. It is shown that the nonlinearity in viscous damping causes a remarkable influence on the Earthquake response in some cases. The reliability and accuracy of the proposed theory are investigated through the comparison with the results by the time-history response analysis to the tuned sine wave as a representative of the long-duration Earthquake Ground Motion.
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Critical response of elastic-plastic SDOF systems with nonlinear viscous damping under simulated Earthquake Ground Motions
Elsevier, 2019Co-Authors: Goki Tamura, Kotaro Kojima, Izuru TakewakiAbstract:Multi impulse with constant time interval is used as a representative of a long-duration Earthquake Ground Motion. An analytical expression is derived for the elastic-plastic response of a single-degree-of-freedom (SDOF) model with nonlinear viscous damping subjected to the “critical multi impulse” which maximizes the response. The fact that only free vibration appears under such multi impulse enables the smart application of an energy approach in deriving the analytical expression for a complicated elastic-plastic response with nonlinear viscous damping. The nonlinear viscous damping characteristic for deformation is approximated in terms of a quadratic or elliptical function. The critical timing of the impulses is found to correspond to the zero restoring-force timing or the maximum velocity timing depending on the input level. It is shown that the nonlinearity in viscous damping causes a remarkable influence on the Earthquake response in some cases. The reliability and accuracy of the proposed theory are investigated through the comparison with the results by the time-history response analysis to the tuned sine wave as a representative of the long-duration Earthquake Ground Motion. Keywords: Civil engineering, Natural hazards, Structural engineerin
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critical steady state response of single degree of freedom bilinear hysteretic system under multi impulse as substitute of long duration Ground Motion
Frontiers in Built Environment, 2017Co-Authors: Kotaro Kojima, Izuru TakewakiAbstract:A set of multiple impulses is introduced as a substitute of many-cycle harmonic waves which represent the long-duration Earthquake Ground Motion. A closed-form expression is derived of the elastic-plastic response of a single-degree-of-freedom (SDOF) structure with bilinear hysteresis under the ‘critical multiple impulse input’. As in the case of elastic-perfectly plastic models, an advantageous feature can be used such that only the free-vibration exists under the multiple Ground Motion impulse and the energy balance approach plays a key role in the derivation of the closed-form expression of a complicated elastic-plastic response. It is demonstrated that the critical inelastic maximum deformation and the corresponding critical impulse timing can be obtained depending on the input level. The validity and accuracy of the proposed theory are confirmed through the comparison with the response analysis to the corresponding sine wave as a representative of the long-duration Earthquake Ground Motion.
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automatic generation of smart Earthquake resistant building system hybrid system of base isolation and building connection
Heliyon, 2016Co-Authors: Masatoshi Kasagi, Masaaki Tsuji, Kohei Fujita, Izuru TakewakiAbstract:A base-isolated building may sometimes exhibit an undesirable large response to a long-duration, long-period Earthquake Ground Motion and a connected building system without base-isolation may show a large response to a near-fault (rather high-frequency) Earthquake Ground Motion. To overcome both deficiencies, a new hybrid control system of base-isolation and building-connection is proposed and investigated. In this new hybrid building system, a base-isolated building is connected to a stiffer free wall with oil dampers. It has been demonstrated in a preliminary research that the proposed hybrid system is effective both for near-fault (rather high-frequency) and long-duration, long-period Earthquake Ground Motions and has sufficient redundancy and robustness for a broad range of Earthquake Ground Motions.An automatic generation algorithm of this kind of smart structures of base-isolation and building-connection hybrid systems is presented in this paper. It is shown that, while the proposed algorithm does not work well in a building without the connecting-damper system, it works well in the proposed smart hybrid system with the connecting damper system.
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bound of Earthquake input energy to building structure considering shallow and deep Ground uncertainties
Soil Dynamics and Earthquake Engineering, 2015Co-Authors: M Taniguchi, Izuru TakewakiAbstract:Abstract The bound of Earthquake input energy to building structures is clarified by considering shallow and deep Ground uncertainties and soil–structure interaction. The Ground Motion amplification in the shallow and deep Ground is described by a one-dimensional wave propagation theory. The constant input energy property to a swaying–rocking model with respect to the free-field Ground surface input regardless of the soil property is used effectively to derive a bound. An extension of the previous theory for the engineering bedrock surface Motion to a general Earthquake Ground Motion model at the Earthquake bedrock is made by taking full advantage of the above-mentioned input energy constant property. It is shown through numerical examples that a tight bound of Earthquake input energy can be derived for the shallow and deep Ground uncertainties.
Fumio Yamazaki - One of the best experts on this subject based on the ideXlab platform.
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horizontal to vertical spectrum ratio of Earthquake Ground Motion for site characterization
Earthquake Engineering & Structural Dynamics, 1997Co-Authors: Fumio Yamazaki, Mehedi Ahmed AnsaryAbstract:SUMMARY Nakamura’s method, which uses a horizontal-to-vertical Fourier spectrum ratio of microtremor, has become popular to determine the predominant period and amplification of a site. In this study, this method is extended for Earthquake Ground Motion recordings using new strong Motion data recorded by JMA-87-type accelerometers. From the analysis of these accelerograms, horizontal-to-vertical Fourier spectrum ratios of a site for di⁄erent Earthquakes are also found to be stable irrespective of magnitude, distance and depth. To establish this fact, attenuation relations of velocity response spectra for horizontal and vertical components are derived for three damping ratios (0, 2 and 5 per cent) using the JMA data. Then the horizontal-to-vertical ratios of the velocity response spectra are obtained. The results show that the horizontal and vertical velocity response spectra are dependent on magnitude, distance and depth, but that their ratios are almost independent of magnitude, distance and depth. However, since the current data set consists of mostly intermediate to far field data, this observation should be limited to records of these distance ranges. Introducing station coeƒcients, representing site amplification, to this relation yields the value comparable to the horizontal-to-vertical Fourier spectrum ratio at a specific site. The stability of the spectrum ratio is explained by the transfer function between the Ground surface and sti⁄-soil outcrop due to S-wave propagation. These results suggest that site amplification characteristics can be evaluated by one-point two-component surface recordings of Earthquake Ground Motion, in a similar manner as proposed by Nakamura for microtremor. ( 1997 by John Wiley & Sons, Ltd.
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attenuation of Earthquake Ground Motion in japan including deep focus events
Bulletin of the Seismological Society of America, 1995Co-Authors: Gilbert L Molas, Fumio YamazakiAbstract:New attenuation equations for peak Ground acceleration and velocity for Japan are developed. The equations are derived using extensive data recorded by the new JMA-87-type accelerometers, which do not require instrumental corrections that the older SMAC-type accelerometers do. Earthquakes with depths up to 200 km are used to make the equation applicable to subduction zone regions, which are common in Japan. Effects of depth and local site on the attenuation are considered simultaneously with the distance dependence and magnitude dependence using a two-stage regression procedure to separate the magnitude dependence from the distance dependence. Since the resulting normal equations become singular, an iterative partial regression algorithm is proposed. It is found that for the same magnitude and distance, peak Ground Motion increases as depth increases. The variation of the station coefficients with respect to the corresponding soil-type classification is quite wide. The station coefficients for the peak Ground acceleration are found to be weakly correlated with the general soil classification, while a stronger correlation was found for the peak Ground velocity. The resulting attenuation relations are given by log 10 PGA = 0 . 2 0 6 + 0 . 4 7 7 M J − log 10 r − 0.00144 r − 0.00144 r + 0.00311 h + c i a , log 10 PGV = − 1 . 7 6 9 + 0 . 6 2 8 M J − log 10 r − 0.00130 r − 0.00144 r + 0.00222 h + c i v , where PGA (cm/sec2) and PGV (cm/sec) are the larger of the peak accelerations and velocities from two horizontal components, MJ is the JMA magnitude, r is the closest distance to the fault rupture, h is the depth, and ci is the station coefficient of the recording station. The mean of the coefficients of the JMA stations is given by ci = 0.
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orientation error estimation of buried seismographs in array observation
Earthquake Engineering & Structural Dynamics, 1992Co-Authors: Fumio Yamazaki, Tsuneo KatayamaAbstract:Array observation is an efficient tool to investigate various characteristics of Earthquake Ground Motion. However, seismographs used in arrays may involve unexpected errors in their orientations. Methods of orientation error estimation were developed in three-dimensional space by comparing recorded Ground Motions at a reference point with those at a checking point. A maximum cross-correlation method and a maximum coherence method were proposed and their accuracy was demonstrated. The Earthquake Ground Motions recorded in the Chiba array and in two other arrays were used in numerical examples. Non-trivial orientation errors were detected for all these arrays. The cross-correlation coefficients and the coherence values between two points increased significantly by correcting the estimated orientation errors.
Julian J Bommer - One of the best experts on this subject based on the ideXlab platform.
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empirical equations for the prediction of the significant bracketed and uniform duration of Earthquake Ground Motion
Bulletin of the Seismological Society of America, 2009Co-Authors: Julian J Bommer, Peter J Stafford, John E AlarconAbstract:Abstract The complete characterization of Earthquake Ground Motion includes the length of the interval of strong shaking as well as the amplitude and frequency content of the time series. There are relatively few published equations available for the prediction of strong-Motion duration from Earthquakes, which may in part be a consequence of the fact that the duration of shaking has generally not been considered in structural engineering. Recognizing that there are many applications for which an estimate of the duration of Ground Motion is needed, this study presents new empirical predictive equations for a number of definitions of strong-Motion duration using the records from the Next Generation of Attenuation (NGA) global database of accelerograms from shallow crustal Earthquakes. The equations can be used to estimate Ground-Motion durations from shallow crustal Earthquakes of magnitude between M w 4.8 and 7.9 at distances up to 100 km from the source.
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empirical equations for the prediction of the equivalent number of cycles of Earthquake Ground Motion
Soil Dynamics and Earthquake Engineering, 2009Co-Authors: Peter J Stafford, Julian J BommerAbstract:Estimates of the number of cycles of Ground Motion expected from Earthquake scenarios are required for the assessment of liquefaction hazard and the hazard of seismically induced landslides. There are currently very few equations available for the prediction of this parameter despite its importance for several geotechnical applications. In this study, the strong-Motion database assembled in the Next Generation of Attenuation (NGA) project is used to derive equations for two different measures of the effective numbers of cycles of Ground Motion as functions of magnitude, distance, and site classification. There are several different measures of the numbers of cycles in an accelerogram but the definition adopted in this study is that based on rainflow-counting, which is applied with both absolute and relative amplitude thresholds.
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an improved method of matching response spectra of recorded Earthquake Ground Motion using wavelets
Journal of Earthquake Engineering, 2006Co-Authors: Jonathan Hancock, Julian J Bommer, Norman A Abrahamson, Jennie Watsonlamprey, Alexandros Markatis, Emma J Mccoy, Rishmila MendisAbstract:Dynamic nonlinear analysis of structures requires the seismic input to be defined in the form of acceleration time-series, and these will generally be required to be compatible with the elastic response spectra representing the design seismic actions at the site. The advantages of using real accelerograms matched to the target response spectrum using wavelets for this purpose are discussed. The program RspMatch, which performs spectral matching using wavelets, is modified using new wavelets that obviate the need to subsequently apply a baseline correction. The new version of the program, RspMatch2005, enables the accelerograms to be matched to the pseudo-acceleration or displacement spectral ordinates as well as the spectrum of absolute acceleration, and additionally allows the matching to be performed simultaneously to a given spectrum at several damping ratios.
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the effective number of cycles of Earthquake Ground Motion
Earthquake Engineering & Structural Dynamics, 2005Co-Authors: Jonathan Hancock, Julian J BommerAbstract:The seismic response of any system that accumulates damage under cyclic loading is dependent not only on the maximum amplitude of the Motion but also its duration. This is explicitly recognized in methods for estimating the liquefaction potential of soil deposits. Many researchers have proposed that the effective number of cycles of the Ground Motion is a more robust indicator of the destructive capacity of the shaking than the duration. However, as is the case with strong-Motion duration, there is no universally accepted approach to determining the effective number of cycles of Motion, and the different methods that have been proposed can give widely varying results for a particular accelerogram. Definitions of the effective number of cycles of Motion are reviewed, classified and compared. Measurements are found to differ particularly for accelerograms with broad-banded frequency content, which contain a significant number of non-zero crossing peaks. The key seismological parameters influencing the number of cycles of Motion and associated equations for predicting this quantity for future Earthquakes are identified. Correlations between cycle counts and different duration measures are explored and found to be rather poor in the absence of additional parameters. Copyright © 2004 John Wiley & Sons, Ltd.
M I Todorovska - One of the best experts on this subject based on the ideXlab platform.
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coherence of sh waves near a semi circular inclusion the role of interference and standing waves
Earthquake Engineering and Engineering Vibration, 2021Co-Authors: Zaniar Tokmechi, Reza S Jalali, M D Trifunac, M I TodorovskaAbstract:We present examples of a controlled numerical experiment that contribute towards understanding of the physical phenomena that lead to the reduction of coherency of strong Earthquake Ground Motion. We show examples for separation distance of 100 m between the two points on the Ground surface, which is in the range of engineering interest. Our examples illustrate the consequences of: (a) standing waves that result from interference of the incident and reflected waves from a near vertical contrast in material properties, (b) standing waves within a concave inhomogeneity (a semi-circular valley in our examples), and (c) smaller Motions in the diffraction zone, behind the inhomogeneity. We show that it is possible to reduce coherency, to the extent observed for recorded strong Earthquake Ground Motion, even by a single inclusion in a half space, for incident Ground Motion that is coherent. We also illustrate the combined effects of geometric spreading and finite fault width, superimposed on the otherwise dominating effects caused by interference. Our examples show reduction of coherence for specific angles of incident waves, while, for other angles of incidence, the coherence remains essentially equal to one.
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a note on the power of strong Ground Motion during the january 17 1994 Earthquake in northridge california
Soil Dynamics and Earthquake Engineering, 2013Co-Authors: M D Trifunac, M I TodorovskaAbstract:Abstract Variations of average and maximum power of strong Earthquake Ground Motion during the 1994 Northridge, California Earthquake were gradual and smooth over distances as large as tens of kilometers. Correlation of the contours of recorded power with the depth of sediments and vertical offsets of the basement rocks along the faults in the Los Angeles basin implies a horizontal flow of Earthquake wave energy through the deep waveguides of this basin. If the fault-to-station distances were to be measured along the three-dimensional wave paths through these sedimentary waveguides, rather than along straight lines emanating from the source, as is common in empirical studies of strong Motion amplitudes, the accuracy of empirical-scaling equations for the prediction of the power of strong shaking could improve significantly.
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a note on energy of strong Ground Motion during northridge california Earthquake of january 17 1994
Soil Dynamics and Earthquake Engineering, 2013Co-Authors: M D Trifunac, M I TodorovskaAbstract:Abstract The average contours of spatial variations of energy of strong Earthquake Ground Motion during the 1994 Northridge, California Earthquake change monotonically and slowly over distances as large as tens of kilometers. Comparison of those contours with the depth of sediments and with vertical offsets of the basement rocks along the faults in the Los Angeles basin implies predominantly horizontal flow of energy through the deep wave-guides of the Los Angeles basin. If the source-to-station distances were measured along the three-dimensional wave paths through these sedimentary wave-guides, rather than along straight lines, as is common at present, the accuracy of empirical scaling equations for prediction of strong-Motion energy would be improved significantly.
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duration of strong Ground Motion during northridge california Earthquake of january 17 1994
Soil Dynamics and Earthquake Engineering, 2012Co-Authors: M D Trifunac, M I TodorovskaAbstract:Abstract Contours of spatial variations of the duration of strong Earthquake Ground Motion during the 1994 Northridge, California Earthquake are smooth over distances as large as tens of kilometers. Visual comparison of those contours with the depth of sediments and with vertical offsets of the basement rocks along the faults in the Los Angeles basin are in excellent qualitative agreement with the trends predicted by the previously published empirical scaling equations of strong-Motion duration. It is argued that if the source-to-station distances were measured along the three-dimensional wave paths through the sedimentary wave-guides, rather than along straight lines as is common at present, the accuracy of empirical scaling equations could be improved significantly.
